Inclusion criteria for physical therapy intervention studies on scoliosis - a review of the literature.

UNLABELLED: There is a wide variation of the inclusion criteria found in studies investigating the outcome of conservative scoliosis treatment. While the application of the SRS criteria for studies on bracing seem useful, there are no inclusion criteria for the investigation of physiotherapy alone. This study has been performed to investigate the possibility to find useful inclusion criteria for future prospective studies on physiotherapy (PT). MATERIALS AND METHODS: A PubMed and (incomplete) hand search for outcome papers on PT has been performed in order to detect study designs and inclusion criteria used. RESULTS: Real outcome papers (start of treatment in immature samples / end results after the end of growth) have not been found. Some papers investigated mid-term effects of exercises, most were retrospective, few prospective and many included patient samples with questionable treatment indications. DISCUSSION: No paper has been found with patients of risk for being progressive followed from premenarchial status until skeletal maturity under physiotherapy treatment alone. Claims made to regard physiotherapy as an evidence based method of treatment are not justified scientifically. An agreement of the scientific community on common inclusion criteria for future studies on PT is necessary. We would suggest the following: (1) girls only, (2) age 10 to 13 with the first signs of maturation (Tanner II), (3) Risser 0-2, (4) risk for progression 40 - 60% according to Lonstein and Carlson. CONCLUSION: There is no outcome paper on PT in scoliosis with a patient sample at risk for being progressive followed from premenarchial status until skeletal maturity. Therefore, only bracing can be regarded as being evidence based in the management of scoliosis patients during growth.

Cerebral regional oxygen consumption and supply in anesthetized cat.

The study involved quantitative measurement of arterial and venous oxygen saturation, oxygen extraction, blood flow, and oxygen consumption in specific areas of the brain. No regional differences in oxygen consumption were found in anesthetized cat brain, and the amount of oxygen available to all regions studied was more than 2.5 times the consumption throughout the brain.

SpineCor vs. natural history - explanation of the results obtained using a simple biomechanical model.

In the recent peer reviewed literature the SpineCor is described as an effective method of treatment for patients with scoliosis. However until recently no prospective controlled end-result study is presented comparing the results obtained with this soft brace to natural history. The objective was to determine whether the results obtained by the use of the SpineCor are better than natural history during pubertal growth spurt. The method employed prospective comparison of the survival rates of SpineCor treatment vs. natural history with respect to curve progression during pubertal growth spurt. 12 Patients with Cobb angles between 16 and 32 degrees (at average 21 degrees) during pubertal growth spurt are presented as a case series treated with the SpineCor. Survival rate of this sample is described and compared to natural history (SRS brace study 1995). All girls treated in both studies were at risk for being progressive with the first clinical signs of maturation (Tanner 2-3). During the pubertal growth spurt most of the patients (11/12) with SpineCor progressed clinically and radiologically as well (at least 5 degrees). Progression could be stopped changing SpineCor to the Chêneau brace in most of the sample described (7/10). The avarage Cobb angle at the start of treatment with the SpineCor was 21.3 degrees, after an average observation time of 21.5 months 31 degrees. At 24 months of treatment time 33% of the patients with the SpineCor where still under treatment with their original bracing concept, at 72 months follow-up time 8 % of the patients with the SpineCor survived with respect to curvature progression. Survival proportion in the SpineCor sample, though was 0.08, while in the natural history cohort it was 0.34. The SpineCor treatment during pubertal growth spurt seems to lead to a worse outcome than observation only. The use of a simple biomechanical model explains that in the brace the compression forces exceed the lateral forces used for the corrective movement. Therefore SpineCor does not seem to be indicated as a treatment during pubertal growth spurt.

Congenital scoliosis - presentation of three severe cases treated conservatively.

UNLABELLED: In view of the very limited data about conservative treatment of patients with congenital scoliosis (CS) available, early surgery is suggested already in mild cases with formation failures in the first three years of life. It is common sense that patients with failures of segmentation will not benefit from conservative treatment at all and the same applies to failures of formation with curves of >50 degrees in infancy. MATERIALS AND METHODS: Two patients with rib synostosis denied surgery before entering the pubertal growth spurt. These patients have been treated conservatively with braces and Scoliosis In-Patient Rehabilitation (SIR) and now are beyond the pubertal growth spurt. One patient with a formation failure and a curve of >50 degrees lumbar has been treated with the help of braces and physiotherapy from 1.6 years on and is still under treatment now at the age of 15 years. RESULTS: Severe decompensation was prevented in the two patients with failure of segmentation, however a severe thoracic deformity is evident with underdeveloped lung function and severe restrictive ventilation disorder. The patient with failure of formation is well developed, now without cosmetic or physical complaints although his curve progressed at the end of the growth spurt due to final mal-compliance. CONCLUSIONS: Failures of segmentation should be advised to have surgery before entering the pubertal growth spurt. In case they deny, conservative treatment can at least in part be beneficial. For patients with failures of formation conservative treatment should be suggested in the first place because long-term outcomes of early surgery beyond pubertal growth spurt are not yet revealed.

Comparison of the kyphosis angle evaluated by video rasterstereography (VRS) with x-ray measurements.

UNLABELLED: Surface topography evaluations are prone to technical errors due to postural sway of the patients measured. The technical error of lateral deviation (rms) and surface rotation (rms) may vary between 15 and 20%, while the kyphosis angle (IP-ITL) has a technical error of only 5% (2,5 degrees), which is comparable to the x-ray measurement. Purpose of this study was to investigate the hypothesis that video rasterstereography can be used for prognostication of a kyphosis patient. MATERIALS AND METHODS: 53 Patients (23 females, 30 males, average age 17 years with a range from 11 to 56 years) undergoing in-patient rehabilitation have been measured with the help of video rasterstereography (VRS) before starting the treatment program and the values for kyphosis angle have been correlated to the kyphosis angle measured on a lateral x-ray (XR) not older than 6 weeks before VRS measurement. 26 had a thoracic Scheuermann, 3 a thoracolumbar, 15 an Idiopathic Kyphosis and 9 a kyphosis of other origin. RESULTS: Average Kyphosis angle XR was 49 degrees (SD 17) and VRS 63 degrees (SD 13). There was a high significant Pearson correlation of 0.78 and a high significant difference of 14 degrees in the t-test (t -9,6, p<0,001). CONCLUSIONS: The kyphosis angle VRS (Vertebra prominens - lower neutral zone of inclination) seems to allow a follow-up of individual kyphosis patients. The XR kyphosis angle according to Stagnara is measured from T4 to the lower end vertebra and therefore is lower than the VRS kyphosis angle measured from T1. The difference found between XR and VRS kyphosis angles may be explained by the angle between T1 (VRS) and T4 (XR) differently used as the upper end vertebra. Therefore the prognostication of an individual patient seems possible within certain limits.

Conservative scoliosis treatment in patients with Prader-Willi syndrome.

UNLABELLED: Patients with Prader-Willi syndrome often suffer from scoliosis of major degrees. Due to current literature surgical intervention seems the gold standard of treatment although the rate of complications in this condition are reported to be significantly higher than in patients with Adolescent Idiopathic Scoliosis. Purpose of this study was to reveal the effects of conservative treatment in this rare patient population. MATERIALS AND METHODS: A case series of patients with this condition has been investigated to estimate as to whether Prader-Willi patients with scoliosis may benefit from conservative scoliosis management. 9 Patients with this condition have been found in our out-patient database. 5 of these retarded patients (3 girls, two boys) today are 19 years and older and therefore are without any significant residual growth. Average Cobb angle was 47 degrees (34 - 66 degrees) at 12 years, average observation time was 6.4 years. RESULTS: Two of the five patients progressed. Average Cobb angle after follow-up was 52 degrees. No progression beyond 70 degrees has been found after cessation of growth. In one patient the curve deteriorated clearly after reducing brace wearing time and therefore was due to non-compliance. CONCLUSIONS: Stabilisation of scoliosis due to Prader-Willi syndrome is possible by means of conservative management. To expose this patient population to the risks of surgical management seems not to be justified.

Postural changes in patients with scoliosis in different postural positions revealed by surface topography.

UNLABELLED: Claims have been made that surface topography is an objective tool, however there are significant postural influences (relatively large technical error due to postural sway) those measurements are prone to. Purpose of this study was to help estimate these influences by measuring patients with scoliosis in three standardized postural positions. MATERIAL AND METHODS: We studied the surface-topography measurement in 100 in-patients with idiopathic scoliosis divided into different age-groups. First group: 7 to 12 years (n=12), second group: 13 to 16 years (n=51), the third 17 to 20 years (n=15) and the fourth >21 years (n=22) (7 males and 93 females). The thoracic Cobb angle was 26.4 degrees, lumbar Cobb angle 25.7 degrees. We investigated the average lateral deviation (rms) and average surface rotation (rms). Measurements were taken one day before the patients left the clinic, after a 3 or 4 week in-patient intensive rehabilitation program (SIR), in three different postures:Normal posture: no specific instructions: standing with feet in an standardized way. Conscious posture: The patients acquired this posture during intensive daily exercising. Corrected posture: The most corrected posture the patients are able to achieve by using specific muscle tension and specific breathing techniques. We compared the results between the different postures. Then we calculated the results for the different age groups. RESULTS: There are significant differences in both parameters tested, some of them more than 40% to 67% greater than the measurement error calculated. The best results were achieved in the second and the third group with the conscious posture, the adult group had the best valued in most corrected posture. For the youngest patients there were no significant changes with the different postures. CONCLUSIONS: Surface measurements can be influenced by artificial postures and therefore cannot be attributed as objective. This is why the surface measurements should be made by someone independent from the treatment process in order to exclude any bias as far as possible. Surface topography may be used for postural monitoring in the rehabilitation process of patients with scoliosis.

Role of propranolol in improvement of the relationship between O2 supply and consumption in an ischemic region of the dog heart.

Several aspects of the myocardial O(2) supply/consumption relationship were determined after coronary artery occlusion and subsequent beta-adrenergic blockade in 16 anesthetized open-chest dogs. Small artery and vein O(2) saturations, and hence extraction, were obtained microspectrophotometrically and combined with radioactive microsphere blood flow determinations to calculate regional myocardial O(2) consumption. Eight dogs remained untreated after coronary artery ligation while another group was given 2 mg/kg propranolol, 10 min after occlusion. Untreated occlusion resulted in decreased arterial and especially venous O(2) saturations, indicating an increased O(2) extraction. Ischemic O(2) consumption was reduced and the subendocardial/subepicardial consumption ratio was reversed (1.26 vs. 0.37) due to the pattern of occluded area flow. Calculated O(2) supply/consumption also decreased. Propranolol produced no significant changes in volume or distribution of flow within the ischemic region while reducing flow, extraction, and consumption in the unoccluded region. The heterogeneity of arterial and particularly venous O(2) saturations within the ischemic region decreased dramatically. Venous O(2) saturations were elevated relative to the control group resulting in a reduced O(2) extraction. The decrease in heterogeneity of arterial and venous O(2) saturations suggest that propranolol eliminates microregions of relatively high O(2) extraction, consumption, and/or a majority of vessels with extremely low flow. This leads to a significant improvement in the O(2) supply/consumption ratio in the ischemic myocardium of the dog. This may be due to a reduction in the heterogeneity and level of beta(1)-adrenergic receptor activity within the heart.

Increased guanylate cyclase activity is associated with an increase in cyclic guanosine 3',5'-monophosphate in left ventricular hypertrophy.

Left ventricular hypertrophy (LVH) produced by aortic valve plication leads to increased myocardial cyclic GMP. We tested whether this was a result of increased soluble guanylate cyclase activity or nitric oxide (NO) synthase and its functional consequences. We used the nitric oxide donor 3-morpholino-sydnonimine (SIN-1) or the NO synthase inhibitor NG-nitro-l-arginine methyl ester (L-NAME) in 12 control and 12 LVH anesthetized open-chest mongrel dogs. L-NAME (6 mg/kg) or SIN-1 (1 microgram/kg per min) was infused into the left anterior descending coronary artery and regional segment work and cyclic GMP levels were determined. In vitro myocardial guanylate cyclase sensitivity (0.43 +/- 0.04 to 0.28 +/- 0.04 mM [EC50]) and maximal activity (10.1 +/- 2.9 to 25.5 +/- 6.5 pmol/mg protein per min) were significantly increased in LVH as compared with control animals in response to nitroprusside stimulation, but cyclic GMP-phosphodiesterase activity was similar. In LVH dogs, basal cyclic GMP was significantly elevated in vivo when compared with controls. Treatment of dogs with SIN-1 resulted in a significant increase in cyclic GMP in control (1.09 +/- 0.12 to 1.48 +/- 0.19 pmol/gram) and a greater increase in the LVH group (1.78 +/- 0.16 to 3.58 +/- 0.71 pmol/g). L-NAME had no effect on myocardial cyclic GMP levels in control or LVH dogs. Segment work decreased in the control group after SIN-1 (1,573 +/- 290 to 855 +/- 211 grams x mm/min). LVH dogs showed no decrement in work as a result of treatment with SIN-1. L-NAME did not cause significant changes in myocardial cyclic GMP, O2 consumption, or work in either control or LVH dogs, but vascular effects were evident. SIN-1 increased cyclic GMP, and with greater effect on LVH; however, this resulted in a decrement in function only in the control group. The greater increased cyclic GMP in LVH dogs is not related to increased NO production, but is related to significantly higher sensitivity and maximal activity of soluble myocardial guanylate cyclase.

Effects of rapamycin on cerebral oxygen supply and consumption during reperfusion after cerebral ischemia.

Activation of the mammalian target of rapamycin (mTOR) leads to cell growth and survival. We tested the hypothesis that inhibition of mTOR would increase infarct size and decrease microregional O2 supply/consumption balance after cerebral ischemia-reperfusion. This was tested in isoflurane-anesthetized rats with middle cerebral artery blockade for 1h and reperfusion for 2h with and without rapamycin (20mg/kg once daily for two days prior to ischemia). Regional cerebral blood flow was determined using a C(14)-iodoantipyrine autoradiographic technique. Regional small-vessel arterial and venous oxygen saturations were determined microspectrophotometrically. The control ischemic-reperfused cortex had a similar blood flow and O2 consumption to the contralateral cortex. However, microregional O2 supply/consumption balance was significantly reduced in the ischemic-reperfused cortex. Rapamycin significantly increased cerebral O2 consumption and further reduced O2 supply/consumption balance in the reperfused area. This was associated with an increased cortical infarct size (13.5±0.8% control vs. 21.5±0.9% rapamycin). We also found that ischemia-reperfusion increased AKT and S6K1 phosphorylation, while rapamycin decreased this phosphorylation in both the control and ischemic-reperfused cortex. This suggests that mTOR is important for not only cell survival, but also for the control of oxygen balance after cerebral ischemia-reperfusion.

Effect of aortic constriction on the oxygen supply-consumption balance in partially ischaemic myocardium.

A study was carried out to determine the effect of distal aortic constriction on the regional oxygen supply-consumption balance in ischaemic and non-ischaemic myocardium. Left anterior descending coronary artery flow was reduced by 50% in anaesthetised mongrel dogs, and half these animals were subjected to distal ascending aortic constriction (ventricular systolic-aortic systolic pressure gradient 50 mm Hg). Blood flows were determined using radioactive microspheres, and arterial and venous oxygen saturations were determined using microspectrophotometry. When left anterior descending artery flow was decreased by 50% tissue flow, as measured by microspheres in the ischaemic region in both control and aortic constricted animals, decreased. Aortic constriction increased flow in the non-ischaemic zone compared with the same region in control animals. The arteriovenous oxygen content difference increased similarly in the ischaemic region in control and aortic constricted animals compared with their respective non-ischaemic zones. Aortic constriction decreased this difference in the non-ischaemic region compared with these same regions in control animals. Oxygen consumption in the non-ischaemic and ischaemic regions of aortic constricted animals was higher than in control animals. The oxygen supply to consumption ratio was lower in the ischaemic zone in both control and aortic constricted animals than in their respective non-ischaemic regions. Aortic constriction does not appear to alter the oxygen supply-consumption balance in the ischaemic myocardium compared with control animals. Thus the increased work performed by the heart in response to the aortic constriction is adequately matched by an increased flow even in the flow restricted region.

Effect of hypercapnia on coronary circulation.

The relative importance of hypercapnia in the control of coronary circulation was examined in 42 anaesthetised open chest rabbits. Coronary blood flow was determined with 15 micron radioactive microspheres. When mean (SD) Paco2 was increased from 38(10) to 76(16) mm Hg in six rabbits, the hypercapnia caused a 62% increase in coronary blood flow. When a similar degree of metabolic acidosis was induced in 12 rabbits for either 15 or 60 min, no changes in coronary blood flow occurred. No increases in coronary blood flow occurred during hypercapnia with propranolol, 2 mg/kg (n = 12), with or without atrial pacing to maintain heart rate. Similarly, carotid denervation prevented the carbon dioxide induced increase in coronary blood flow in six rabbits. Haemodiluted rabbits (n = 6) with a 40% replacement of blood showed no changes in coronary blood flow with hypercapnia. This was due to the 22% decrease in systolic pressure-time index, despite their intact sympathetic nervous system and reduced Bohr shift. Therefore, although carbon dioxide is a coronary vasodilator, both direct vasodilatation and sympathetic adrenergic activation must be intact in order for coronary blood flow to be increased.

Regional O2 consumption in canine left ventricular myocardium in experimental acute aortic valvular insufficiency.

Moderate and severe acute aortic valvular insufficiency (AVI) were produced for 30 min in anesthetised, open-chest dogs, in order to measure O2 consumption in subepicardial (EPI) and subendocardial (ENDO) regions of the left ventricular free wall. Regional O2 consumption (MVO2) was determined from regional O2 extraction and blood flow data determined by absorbence microspectrophotometry and radioactive microspheres. In all groups, venous saturations were lower and O2 extractions higher in the ENDO than in the EPI. Oxygen extractions increased in both regions in both severities of AVI, but more so with severe AVI. The ENDO became perfused relative to the EPI with increasing severity of AVI. Left ventricular MVO2 increased with AVI; however, ENDO MVO2 increased less than EPI MVO2. ENDO/EPI blood flow ratios decreased from 1.21 to 0.93 in moderate AVI and to 0.76 in severe AVI. ENDO/EPI MVO2 ratio decreased from 1.44 in controls to 0.94 in moderate and 0.54 in severe AVI. The ENDO/EPI MVO2 ratios began to decrease when DPTI/SPTI was less than 0.4 to 0.5. We conclude that AVI increases MVO2, but the ENDO cannot maintain its MVO2 relative to EPI because of proportionately less ENDO flow, and maximal O2 extraction.

Effect of moderate arterio-venous shunt on regional extraction, blood flow and oxygen consumption in the dog heart.

The effects of a moderate sized arterio-venous shunt on the relationship of oxygen supply to consumption were studied on a regional basis in the dog left ventricle. Experiments were conducted on fourteen hearts, seven in control pentobarbital-anaesthetised, open-chest dogs and seven in dogs with an additional abdominal aorto-caval shunt. Regional oxygen extraction was determined by a microspectrophotometric method and coronary blood flow was measured with radioactive microspheres. The shunt, when opened, allowed cardiac output to increase by 50%. This was accomplished by increasing stroke volume, not heart rate. In control animals the subendocardium exhibited higher oxygen extraction, coronary flow, and oxygen consumption than did the subepicardium. There were no differences between base and apex. In open-shunt animals, subepicardial-subendocardial differences in extraction, flow and consumption were abolished. Subepicardial values for these in shunt animals were not different from the values obtained for the subepicardial values of controls. The subendocardium of shunt animals exhibited significant differences between base and apex for blood flow and oxygen consumption. There was a significant difference in subendocardial oxygen consumption between groups, the effect of the arterio-venous shunt being to reduce subendocardial consumption, especially in the apex, without reducing subepicardial oxygen consumption.

Increased myocardial microvascular utilisation and flow during atrial pacing.

To determine the influence of heart rate on regional coronary flow, the coronary vascular and microvascular responses to increased heart rate were examined in anaesthetised open chest New Zealand white rabbits. Coronary blood flow was measured with labelled microspheres. Fluorescein isothiocyanate (FITC)-dextran (150 mg.kg-1) was given to mark the perfused microvessels. The FITC-dextran was given at various intervals before removal of the heart. Alkaline phosphatase stain was used to locate the total microvasculature. Increase in heart rate from 272(SD23) to 339(13) beats.min-1 increased the coronary blood flow from 198(56) to 288(82) ml.min-1.100 g-1. The subendocardial/subepicardial flow ratio was not altered by pacing. Total capillary density averaged 2508(363).mm-2 and arteriolar density was 1.74(4.1).mm-2. There were no significant regional or treatment differences in these values. The increase in blood flow with pacing was accompanied by a uniform increase in the percentage of the microvasculature perfused in the subepicardial and the subendocardial layers of the left ventricular free wall, from 58(6)% to 75(10)% for capillaries and from 54(17)% to 81(19)% for arterioles. These results show that enhanced heart rate increases the coronary blood flow and the density of the perfused microvessels uniformly across the ventricular wall. Thus both the coronary vascular and microvascular reserves are used in the rabbit heart during tachycardia.

Dependence of spatial heterogeneity of myocardial blood flow on mean blood flow rate in the rabbit heart.

The relationship between spatial heterogeneity of myocardial blood flow and the rate of perfusion was examined in anaesthetised-chest rabbits. Blood flow determinations employed the radioactive microsphere technique. Five tissue samples were obtained from each of four regions of the left ventricle: left septum, right septum, subendocardium and subepicardium. Standard deviation (SD) and the coefficient of variation (CV = SD/mean flow x 100), an index of spatial heterogeneity, were computed. A wide range of mean coronary flows was obtained in seven groups by inspiration of room air, 8% O2, 8% O2 and 10% CO2, 100% O2, 100% O2 and hyperventilation, and by administration of adenosine or chromomar HCl. Significant differences in CV were found between treatment groups at the upper and lower ends of the flow range. A significant positive linear correlation between overall SD and mean coronary flow was found (r = 0.760). A significant inverse linear relationship between CV and mean flow was found over the entire range of flows studied (r = -0.482). An improved correlation between CV of calculated coronary vascular resistance and mean vascular resistance (r = 0.742) amongst these treatments suggests that spatial heterogeneity is better described by the variability in calibre of large arterioles. This decreased heterogeneity accompanying high flows or reduced vascular resistance may be beneficial in terms of O2 supply and demand under conditions of myocardial stress.

Morphometric study of the total and perfused arteriolar and capillary network of the rabbit left ventricle.

A method has been developed to simultaneously and regionally determine several morphometric indices of both the total and perfused arteriolar and capillary beds of the rabbit heart on a quantitative basis. A high molecular weight fluorescein isothiocyanate (FITC) dextran, was injected into the femoral vein of an anaesthetised open chest rabbit. The hearts were removed and frozen in liquid N2 within 14 s after this injection. Sections, 2 micrometers thick, were obtained from the left ventricular wall and the fluorescence photographed to detect perfused arterioles and capillaries. The sections were then stained to visualise the total arteriolar and capillary network. Standard morphometric techniques were employed to study the total and perfused microvasculature. The method was validated to show that it did not alter the microvasculature of the heart, that both the total and perfused microvasculature could be visualised, and that there was little tissue shrinkage. The study found no significant subepicardial vs subendocardial differences in either the total or perfused capillary of arteriolar networks. The total capillary bed had very much larger morphometric indices than the total arteriolar bed. The percentage of the microvasculature perfused ranged from 55 to 64% of the capillary and 51 to 56% of the arteriolar beds for the various indices. Thus at least a part of the control of capillary perfusions is at the level of the arteriole. There was an almost twofold functional reserve in the microvasculature of the heart which could be mobilised by asphyxia.

Local adenosine infusion and myocardial oxygen supply and consumption in reperfused canine myocardium.

STUDY OBJECTIVE: The aim was to determine whether a local infusion of adenosine could increase coronary blood flow to restore fully the O2 supply to consumption balance in reperfused myocardium. DESIGN: The left anterior descending coronary artery was occluded for 2 h followed by a 4 h reperfusion with and without simultaneous local infusion of adenosine (50 micrograms.kg-1.min-1). In another group, adenosine was infused for 4 h. Small artery and vein O2 saturations (microspectrophotometry) and regional flow (radioactive microspheres) were determined. SUBJECTS: 25 anaesthetised open chest mongrel dogs, divided in three groups, were used in this study. MEASUREMENT AND MAIN RESULTS: In the central group, 2 h occlusion decreased regional blood flow below normal. After 4 h of reperfusion, blood flow was less than normal in the affected area, at 57(SD39) affected v 85(31) ml.min-1.100 g-1 control. O2 extraction was higher in the reperfused area, with 61% of veins having O2 saturations less than 35%. For the experimental group, adenosine was infused into the left anterior descending artery at a dose of 50 micrograms.kg-1.min-1. Adenosine coupled with reperfusion increased regional blood flow above control in the affected area, to 267(238) ml.min-1.100 g-1, but this was less than was found with adenosine alone. O2 extraction in this area was lower than with reperfusion alone, with only 1% of veins having O2 saturations less than 35%. CONCLUSIONS: A large flow reserve is present in reperfused tissue and the low O2 saturations found in reperfused myocardium cannot be due to vessel blockage (greater than 20 microns in diameter). Thus local adenosine can be used to mobilise the reserve to improve the O2 supply to consumption balance.

Augmented efficiency of regional myocardial work by ouabain.

STUDY OBJECTIVE: The effect of ouabain on regional myocardial mechanics and corresponding regional myocardial oxygen consumption was investigated. DESIGN: Regional myocardial segment length (ultrasonic dimension crystals) and force development (miniature strain gauge) were measured. The integrated multiples of myocardial shortening by corresponding force during an averaged beat was used to express regional segment work (= area under the systolic portion of the length-force loop). External cardiac work was calculated from aortic blood pressure and cardiac output. Global and regional myocardial O2 consumption (MVO2) were evaluated at baseline and during intravenous infusion of ouabain (7 micrograms.kg-1.min-1). Regional coronary blood flow was measured with radioactive microspheres, and microspectrophotometry of frozen myocardial biopsies was used to evaluate O2 saturation in small arteries and veins. These variables were used to calculate regional myocardial MVO2. Arterial and coronary sinus O2 saturation was used to calculate global left ventricular O2 consumption. Myocardial efficiency was expressed as regional work/regional myocardial MVO2. SUBJECTS: Ten open chest anaesthetised dogs, weight about 20 kg, were used. MEASUREMENTS AND MAIN RESULTS: Ouabain increased regional myocardial segment work [from 5291(SEM 1067) to 8916(2338) mm.g-1.min-1] to a greater extent than regional myocardial MVO2 [from 6.33(0.75) to 8.54(0.75) ml O2.min-1.100 g-1]. Regional efficiency was increased from 734(78) to 1036(160) g.mm.ml O2(-1).100 g-1. External efficiency was not raised. Percent shortening was increased to a greater extent than peak force development (+76% v + 38%), possibly indicating increased myocardial compliance. The length-force loop was shifted upward and to the right. CONCLUSIONS: Ouabain increases regional efficiency of myocardial contraction.